U-shaped fluorescent lamps are characterized by a 180-degree bend on one end joining a pair of longitudinally extending leg members which terminate in bases with electrical contacts which plug into electrical connecting sockets mounted in a mount, but arranged on the same end as contrasted with two typical straight lamps which each have a pair of bases and a pair of sockets mounted on opposite ends. The U-shaped lamps have a number of applications but are particularly useful in the contemporary commercial lighting industry. In the case of a U-shaped lamp as contrasted with a straight lamp, one U-shaped lamp does the work of two short straight lamps which means fewer ballasts and sockets must be purchased and installed. U-shaped lamp ends are only inches apart in one raceway and are not separated by many feet, reducing wiring requirements. Since only a single ended lamp support is required, less raceway work is needed. Accordingly, for many applications fewer U-shaped lamps than straight lamps can be utilized for doing the same illumination job with savings of materials, ballasts, sockets, labor, and energy.
However, the U-shaped lamp with its 180-degree bend on one end with the legs extending therefrom has been generally more fragile because of the bend, and accordingly considered to be more difficult to handle than a single straight lamp. The problem has arisen in handling and shipment as well as in installation. Little leeway is tolerated in lateral movement of the legs, and the lamps are particularly vulnerable when being plugged into dual sockets in the mount, because undue pressure on one leg in entry to the socket may fracture the lamp bend. This is particularly true when the lateral movement of legs is toward each other putting the glass on the outside of the bend in tension. Since glass is weakened by tension, the thinned outside of the bend is most vulnerable when the legs are moved toward each other in handling, shipping, carrying to the fixture for installation or while installing.
In order to prevent possible breakage problems and to ensure the spacing of the two bases or of the two leg members, it is well known to reinforce the free ends of such lamps and prevent them from being compressed or spread apart.
A one-piece slip-on brace member is disclosed in U.S. Pat. No. 3,337,035 issued to Pennybacker on Aug. 22, 1967. The brace is made from stiff wire and is provided with arcuate loops at each end that are slipped over and compressively grip the legs of the U-shaped envelope. While braces which encircle the envelope portions of the lamp leg members achieve the desired purpose, they are not entirely satisfactory since such braces cast shadows and/or decrease the amount of light output from the leg members.
Other types of braces or straps are known which either engage or interconnect with the lamp bases. For example, it is well known to provide each base with a metal clamp around its circumference in such manner that the flaps of the respective clamp point towards each other in the direction of the connection line of the two bases. The two clamps are then interconnected by means of a crossbar which is placed with its respective ends between the pair of clamp flaps and is riveted in place. Such an arrangement is similar to those illustrated in FIG. 2 of U.S. Pat. No. 3,548,241 issued to Rasch et al on Dec. 15, 1970 and in U.S. Pat. No. 4,422,010 issued to Hammer on Dec. 20, 1983 (elements 22,23,24).
U.S. Pat. No. 3,579,174, issued to Gilbert, Jr. on May 18, 1971, discloses another type of brace for U-shaped fluorescent lamps which interconnects with the lamp bases. This structure provides a notch in the circumference of each base, the notches facing one another and extending in the plane common to the base pins. The notched bases are interconnected by a bar which has a groove at its ends. The grooved ends engage in the respective notch at the base circumference. The assembly is then sealed with cement to the lamp ends.
U.S. Pat. No. 3,602,755, issued to Hoeh on Aug. 31, 1971, discloses a bracket with semicircularly or circularly curved ends as the spacer member; the straight-line portion of the bracket is passed through an aperture in the circumference of the respective base cap which is flush with the base pins so that the curved ends of the bracket come to lie internally of the base cap. A ring-shaped binding agent (cement ring) is introduced into the base caps and the whole assembly is sealed to the lamp ends by heating.
U.S. Pat. No. 4,217,630, issued to Albrecht on Aug. 12, 1980, teaches a spacer member which is formed to interconnect with a pair of specially designed base caps. Each cap has a pair of substantially parallel radially outwardly projecting members having extending means therebetween. The spacer member has respective ends slidably engagable between the outwardly projecting members for positive engagement with the extending means.
Braces which engage or interconnect with the lamp bases generally require either an aperture or notch to be formed in each of the bases or specially designed base caps.
In addition to the above-mentioned disadvantages, some of the prior methods employed do not easily accommodate variations in the outside diameter of the bases or are not readily adaptable for attachment to U-shaped fluorescent lamps using automated equipment.